This invention relates to the handling, including squaring, of conveyed shingled sheets and is adapted to compliment concepts such as those disclosed in U.S. Pat. No. 4,200,276.
In that patent, a web of corrugated paperboard or the like is first cut into a plurality of individual sheets. The sheets are then conveyed to a shingler which forms them into overlapping arrangement. The shingles are then conveyed to a stacker for subsequent stacking and discharge. In the device of the patent, the sheets are conveyed at varying speeds through the use of an automatic control system.
A problem arises in the transportation of the shingled sheets between the shingler and stacker. After discharge from the shingler, the shingled sheets sometimes tend to twist or skew sideways on the supporting conveyor. If the shingled sheets enter the stacker in skewed condition, they do not feed straight in to the stacker throat, resulting in possible bending or other damage to the sheets.
Various solutions to the problem have been proposed and adapted in the past. Examples are illustrated in U.S. Pat. Nos. 4,273,325 and 4,598,901. It has also been proposed to convey sheet material along a conveyor and between side mounted belts or the like which may, in some instances, tend to keep the material longitudinally aligned.
It is an object of the present invention to provide for improved handling of conveyed sheet material, especially at high conveying speeds. It is a further object to provide for controlled and essentially automatic handling and squaring of sheets in an improved manner.
In accordance with various aspects of the invention, a shingle handling and squaring device is disposed between a sheet shingler and stacker and mounted above a stack infeed conveyor. The device includes side carriages, each of which carries a pair of freely rotatable longitudinally in-line tamping rollers or wheels, the peripheries of which are adapted to engage an edge of the traveling sheet material. The wheels are mounted for rotation about generally vertical but slightly inclined axes and have tapered peripheries so that the wheels nevertheless present truly vertical faces to the sheet material.
In addition, when the stacker infeed nip roll is raised by the entry of shingled sheets, a device is provided to release the nip roll from the sheets to prevent binding. While the nip roll is released, the side carriages are moved transversely inwardly toward the sheet edges in a unique manner such that even off-center sheets are automatically and properly engaged and squared by the tamping wheels before the stacker infeed nip roll is reengaged with the sheets.
Furthermore, an automatic jam detection and releasing arrangement is associated with the upstream wheels in the present embodiment, and which is responsive to excessive upward wheel lifting about a transverse axis.